The present invention relates to a conveyance robot which conveys an article among a plurality of vacuum containers in a CVD apparatus, an etching apparatus, a sputtering apparatus or the like for manufacturing an electron device such as semiconductor integrated circuit, or in a testing apparatus or the like.
In the prior art, systems for conveying a workpiece within a vacuum chamber are classified into a mechanical type and a magnetic floatation type.
The mechanical type includes a robot in which, as shown in FIGS. 4(a) and 4(b), levers 27 and gears 28 are employed for a rectilinear movement axis (R-axis) for moving the workpiece rectilinearly. For a vertical movement axis (Z-axis) for moving the workpiece up and down, a gear 29 and a guide 30 are disposed in a vacuum as shown in FIG. 5. Regarding a rotation axis (.theta.-axis), as shown in FIG. 6, a gear 32, etc. in the vacuum are rotated in such a way that power is transmitted from the atmospheric air side by a magnetic seal unit 31 employing a magnetic fluid.
On the other hand, the magnetic floatation type includes a conveyance system having the two axes of a .theta.-axis and a Z-axis, in which a magnet coil section exists in a vacuum, and a conveyance system in which a magnet coil section exists outside a vacuum, but which has only an R-axis. In the former system, gases are emitted due to the heat of the magnet coil section. With the latter system, the extent of the movement of the workpiece is limited by the low degree of freedom.
In the prior-art system of the mechanical type, the drive mechanism elements which have sliding parts, and rolling parts, such as gears, screws and bearings, are located in the vacuum. This leads to the problem that the parts frictionally wear off to produce microscopic particles, which pollute the vacuum atmosphere. In addition, as an expedient for enhancing the wearproofness, thin films of soft metal such as gold, silver or lead are formed on sliding surfaces and rolling surfaces, or boron nitride, silicon nitride, molybdenum disulfide, or the like is applied in the form of thin films so as to utilize solid lubrication. In this case, the durabilities of the films are problematic. Moreover, since the friction factors substances are generally greater in a vacuum than in the atmospheric air, the motions of the sliding parts and the rolling parts are liable to be hampered.
Meanwhile, even with the magnetic floatation type, when the magnet coil section exists in the vacuum, the gas emission from a winding portion forms a pollution source. There is also an example wherein a winding portion is molded with a resin. That example, however, has the problem that the pollution of the vacuum is unexpectedly worsened because the component molecules of the resin vaporized by a temperature rise ascribable to baking exhibit much longer mean free paths in the vacuum than in the atmospheric air.